Hannu Hietalahti Kevin Holley Stephen Hayes Brian Daly

© 3GPP 2009 Mobile World Congress, Barcelona, 19th February 2009© 3GPP 2010 3GPP PWS presentation 1

Hannu HietalahtiKevin Holley

Stephen HayesBrian Daly

PWSPublic Warning System

IETF #79, 7 – 12 Dec, 2010, Beijing, China


Contents

Cell Broadcast Service OverviewCurrent status of PWSPWS Service requirementsCell Broadcast ServicePWS Technical overview• Use case• Details

ExtensibilityMessage IdentifiersRegional StandardsCMAS architecture and call flow exampleSummary


Current status of Public Warning System

PWS comprises public alert services in 3GPP• Earthquake and Tsunami Warning System ETWS (Rel-8)• Commercial Mobile Alert System CMAS (Rel-9)• EU-Alert requirements are being studied (Rel-11)

Global service• Warning categories must be defined globally• Detection of the warning categories must be global for roaming users• Applicable in 3GPP systems over GSM, UTRAN and LTE radio

Specification references• Stage 1 in 3GPP TS 22.268 (Requirements)• Stage 2 in 3GPP TS 23.041 (CBS, Message Identifier coding)• Stage 3 in 3GPP TS 25.304, 25.331, 36.304, 36.331, 45.002, 44.018

(Radio interface)


Service requirements (from 3GPP TS 22.268)

Broadcast Warning Notifications to multiple users simultaneously• Geographical notification area is specified by the Warning Notification Provider• Roaming subscribers must be supported • Concurrent broadcast of multiple Warning Notifications • with no acknowledgement required

PWS capable terminals in idle mode shall be able to receive broadcast warnings • User may opt-out from certain alert categories

Warning Notifications languages are determined by regulatory requirements Warning Notifications are processed by PWS on a first in, first out basis, subject to regulatory requirementsReception and presentation of Warning Notifications to the user shall not pre-empt an active voice or data session.Current implementation requirement is up to 90 7-bit charactersTypical contents of the warning:

• Event Description • Area Affected• Recommended Action • Expiration Time (with time zone) • Sending Agency


Cell Broadcast Service (CBS)

CBS is defined in 3GPP TS23.041• CBS can cover different services that are independent of each other• PWS uses CBS in GSM and UTRAN• In LTE the messages are encoded according to CBS rules, but distribution at the radio

interface is LTE specificUnacknowledged broadcast to all CBS-capable mobiles within a particular region

• defined geographical areas known as cell broadcast areas• may comprise of one or more cells, up to the entire network

CBS messages may originate from a number of Cell Broadcast Entities (CBEs) through an operator’s Cell Broadcast centre (CBC)

• CBS messages are sent from the CBC to the cells, in accordance with the CBS's coverage requirements

Maximum capacity ranges from GSM 93 7-bit characters to LTE 316 characters• Message segmentation is possible (15 – 64 segments)

A CBS message is identified by a message identifier and serial number• Can be used by the mobile to “screen” which messages are received• Also to identify and ignore re broadcasts of already received messages• 3GPP manages the message identifiers

CBS messages may be broadcast cyclically by the cell at a frequency and for a duration agreed between the operator and the information provider


Technical overview, use case(Figure from 3GPP TS 22.268)

Key points:• Interface provided to Government authority to submit alert messages• Government authority is responsible for interface to and authentication of alert originators• Security against fake alarms, operator must authenticate alert issuer at interface C• Support for all terminals in the affected geographical area, including roaming users and terminals

sourced from other countries• Distribution mechanisms at radio interface differ between GSM, UTRAN, LTE but are all based on

broadcast mechanisms


Technical overview, details

Radio procedures for broadcasting in 3GPP radio access technologies• Common paging or SysInfo change or CBS

Distribution area• Geographical selectivity is based on network topology• Alert codes are globally defined• Detection of alert categories is not restricted to physical distribution channel

at radio interface but part of PWS service• Paging to wake up the terminal to listen to broadcast information• Mutual authentication to avoid MiM and playback attacks

Data coding scheme is critical for compatibility and mobility• Message Identifier corresponds with alert category

• Message Identifiers to be received can be pre-configured on USIM or by the user• Language code• Default 7-bit coding with several language specific extensions or 16-bit UCS2

coding for other languages• Sequencing to distinguish between different messages


PWS extensibility

Message identifier ranges are assigned for different broadcast use cases• MI 0 – 999 are defined by GSMA for Flash messages, weather reports, traffic reports, date &

time, etc • http://gsmworld.com/documents/SE15330.pdf

• MI 1000+ are defined by 3GPP for specific services, among them PWS• MI values 1100 – 18FF are reserved for PWS use• More than 2000 code points not assigned yet• ME application configures the reception of the MIs related with the service• Reception of any MI can be configured on USIM by the HPLMN operator

Legacy terminal processing of unforeseen data is normatively specified and thus predictable

• alert category, character set, broken sequence, etc.All alert categories shall be globally unique

• National or regional exceptions cannot change the meaning of alert code• Japanese Tsunami alert code cannot be re-used for avalanche warning in Switzerland• CMAS Presidential Level Alert code point can be re-used for EU-Alert 1

• Additions to existing codes are possible• National extensions must be defined globally

http://gsmworld.com/documents/SE15330.pdf


Message Identifiers (3GPP TS 34.041)Decimal Hex Meaning

0 – 999 0000 – 03E7 Allocated by GSMA (see GSMA PRD SE.15 http://gsmworld.com/documents/SE15330.pdf )

... ... …

4352 1100 ETWS CBS Message Identifier for earthquake warning message.

4353 1101 ETWS CBS Message Identifier for tsunami warning message.

4354 1102 ETWS CBS Message Identifier for earthquake and tsunami combined warning message.

4355 1103 ETWS CBS Message Identifier for test message.Normal UE silently discards this message. Test UE may may display its contents.

4356 1104 ETWS CBS Message Identifier for messages related to other emergency types.

4357 – 4359 1105 - 1107 ETWS CBS Message Identifier for future extension.

... ... …

4360 - 4369 1108 - 1111 Intended for standardization in future versions of this document. These values shall not be transmitted by networks that are compliant to this version of this document. If a Message Identifier from this range is in the "search list", the ME shall attempt to receive this CBS message.

4370 1112 CMAS CBS Message Identifier for Presidential Level Alerts. Not settable by MMI.

4371 1113 CMAS CBS Message Identifier for Extreme Alerts with Severity of Extreme, Urgency of Immediate, and Certainty of Observed. Settable by MMI as per CMAS subscriber opt-out requirements

... ... …

4383-4399 111F-112F CMAS CBS Message Identifier for future extension.

4400 - 6399 1130 – 18FF CBS Message Identifier for future PWS use. These values shall not be transmitted by networks that are compliant to this version of this document. If a Message Identifier from this range is in the "search list", the ME shall attempt to receive this CBS message.

6400 – 40959 1900 – 9FFF Intended for standardization in future versions of this document . These values shall not be transmitted by networks that are compliant to this version of this document. If a Message Identifier from this range is in the "search list", the ME shall attempt to receive this CBS message.

... ... …


Regional StandardsETWS, CMAS, EU-Alert

ETWS requirements are defined by Japanese requlator, but not normatively referenced from 3GPP specifications• 3GPP TS 22.268 captures the 3GPP system requirements for ETWS

CMAS is defined under FCC CFR 47 Part 10 Rules in the U.S.CMAS Standards developed by ATIS and TIA:• J-STD-100, J-STD-101, ATIS-0700006, ATIS-0700007, ATIS-0700008,

ATIS-0700010EU-Alert requirements are specified in ETSI ETS 102 900


CMAS architecture

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CMAS Call Flow Example

CMSP Gateway in the operator network receives the CMAS alert from the government entityThe alert is passed to the operator’s cell broadcast centre (CBC) which identifies the cell site(s) to broadcast the alertThe alert is broadcast using 3GPP PWS


Summary

PWS was designed by 3GPP as a global solution for issuing public warnings over 3GPP mobile systemsPWS is designed to allow extendable set of national and regional specific alerts while maintaining global uniquenessPWS is a service for alerting and updating the user of emergency situations in a timely, secure, and geographically selective mannerPWS architecture • provides interface towards public authorities who generate and authorize

the warnings• uses common PWS broadcast and message coding capabilities• uses radio specific cell broadcast procedures in GSM, UMTS and LTE• is extendable in future 3GPP enhancements

Hannu Hietalahti Kevin Holley Stephen Hayes Brian Daly

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